SANFORD, Fla. -- Attorneys in the George Zimmerman murder trial are closing in on an important milestone in the jury selection process.

They need a pool of 30 potential jury members in order to move past questioning that deals strictly with pretrial publicity.

Right now, the pool sits at 20 with six more potential jurors expected to testify on day four of the trial Thursday.

Once the 30 jurors are obtained that have not been dismissed for cause, attorneys intend to ask more probing questions about the jurors' lives and beliefs.

A total of 10 jurors, six main jurors and four alternates, are needed to begin trial, but none have been seated so far.

More than 70 have also been dismissed since jury selection began Monday.

Zimmerman is on trial for the February 2012 shooting death of Trayvon Martin, 17, in Sanford, Florida.

He is claiming self-defense and has pleaded not guilty.

There is no timeline set for when a jury must be seated. Many legal experts say the selection process could take upwards of three weeks.